Environmentally controlled greenhouse

ABSTRACT

A greenhouse and a method for controlling the environment of the interior space of the greenhouse is disclosed. The greenhouse (10) includes an interior insulative panel (22,23) and an exterior reflective panel (26) capable of insulating the interior of the greenhouse and reflecting sunlight into the interior. The greenhouse also includes a closed-system heat exchanger (30,31) having a plurality of spaced water-impermeable water flow passageways (60) through which water flows by gravitational forces and having a means for blowing air (65) between the water flow passageways (60) such that the air does not contact the water and such that the air is either heated or cooled by the water. In addition, the heat exchanger (30,31) may include a water discharge (71) and/or a gas discharge for the control of humidity and gas levels within the greenhouse. Finally, the greenhouse includes hydroponic plant beds (34,35) disposed on top of the heat exchangers (30,31) and hydroponic solution tanks (36,37) along the outer interior walls of the greenhouse. The floor plan of the greenhouse allows easy access to all plants and assists in maintaining the temperature within the greenhouse due to the presence of the hydroponic solution tanks without significantly reducing the area available for plants. Such a greenhouse is inexpensive to operate and maintain and may be used to extend the growing season of seasonal plants throughout the calendar year.

FIELD OF THE INVENTION

This invention relates to environmentally controlled greenhouses, and,in particular, to a greenhouse which extends the growing season ofseasonal plants to last virtually throughout the calendar year.

BACKGROUND OF THE INVENTION

Greenhouses generally provide an environment which assists infacilitating the growth of many types of vegetation. In addition to theprovision of optimum sunlight, the greenhouse's interior atmosphere maybe controlled by other means. A heating or cooling system may beinstalled to compensate for variations from the desired interiortemperature created by too little or too much sunlight. Reflectivepanels and insulating panels have also been pivotally attached togreenhouse wails and ceilings to assist in controlling the interiortemperature. Despite the implementation of these technologies, the useof a greenhouse to extend the growing season of seasonal plants, such asstrawberry plants, at an affordable cost, has been illusive. Generally,the requirement for a heating and cooling system sufficient to create asuitable environment for these environmentally sensitive plants hasresulted in prohibitively expensive operating costs. Thus, it isdesirable to develop an environmentally controlled greenhouse which maybe utilized to extend the growing season of such plants and which isenergy efficient and inexpensive to operate so that the farmer mayprofit from the sale of the plants or the fruit they bear.

One mechanism used to retain heat in the interior of the greenhouseduring the nighttime hours or low sunlight conditions and to alleviatethe problem of excess heating during warm weather comprises theplacement of a translucent ceiling within the interior of thegreenhouse. A movable panel is placed on top of the translucent ceilingduring conditions of nighttime or low sunlight conditions. The panel isthen moved away from the ceiling to allow sunlight to infiltrate throughthe translucent ceiling when sunlight or warmth in the greenhouse isdesired. The translucent ceiling reduces the volume of space thegreenhouse heating and cooling system must control, thereby reducingcost. Examples of translucent ceilings with movable panels include theinventions disclosed in U.S. Pat. Nos. 4,242,833 and 4,249,340. U.S.Pat. No. 4,552,212 discloses a solar heating and cooling system for abuilding which includes adjustable ceiling doors or panels which may beplaced over the building's translucent ceiling to retain heat therein.U.S. Pat. No. 4,706,420 discloses pivotable insulative panels over thevertical exterior walls of the greenhouse and a retractable canopy whichcovers the roof of the greenhouse to thereby retain heat within thegreenhouse.

To assist in directing sunlight into the interior of the greenhouse avariety of mechanisms have been used. For example, the greenhousedisclosed in U.S. Pat. No. 4,414,784 may be attached to a balcony of anapartment. Since all balconies may not be oriented to properly takeadvantage of the optimum sunlight conditions for plant growth, areflector panel is provided which aids in directing sunlight into theenclosure of the greenhouse. Similarly, the greenhouse disclosed in U.S.Pat. No. 5,056,259 includes a roof whose incline may be adjusted and ascreen which may be used to control the amount of sunlight directedtoward the interior of the greenhouse. U.S. Pat. No. 4,929,444 disclosesa solar building with a roof that may be adjusted to optimize the solarcollection panel on the roof.

It is desirable to provide a greenhouse which is able to optimize theamount of sunlight required for the growth of the plants therein as wellto retain the heat within the greenhouse according to prescribed optimumconditions for the types of plants within the greenhouse. Such agreenhouse may require a supplemental heating and/or cooling system,depending on the climate and the weather at a particular installation.

As previously mentioned, it is known to place conventional heatingand/or cooling systems within the interior of a greenhouse to assist inmaintaining the desired temperature therein. Such systems usuallyconsume considerable energy under extreme exterior conditions, such aslow sunlight coupled with low exterior temperature or intense sunlightcoupled with high exterior temperature, so as to make their use inseasonal climate prohibitively expensive when trying to extend thegrowing season of seasonal plants. Electric and gas heaters or airconditioners utilize the energy source to affect a change in theinterior temperature. Heat pumps are comprised of a compressor which isexpensive to operate, and are sometimes ineffectual without theprovision of an additional source of heat, under extreme conditions.Thus, it is desirable to provide a means for heating and cooling theinterior of a greenhouse which is not prohibitively expensive tooperate, is inexpensive to maintain, and which requires littlemaintenance or repair.

It is also desirable to provide an auxiliary heating and/or coolingsystem which is a closed system. That is, under ideal circumstances, theheating and cooling system should be able to operate within the interiorof the greenhouse and not require that significant amounts of externalair be brought into the interior of the greenhouse. Such external air isgenerally not optimum for the plant growth. For example, the externalair may not be of the desired temperature, humidity or gas content asthat of the interior of the greenhouse. Therefore, energy must beexpended to "process" the external air to match that of the greenhouse'sinterior air.

Of importance in the use of a greenhouse is the actual floor plan of itsinterior space. Not only is it desirable to produce as much vegetationas possible, but it is also desirable to provide a greenhouse whosecontents are arranged to permit easy access to the plants within theinterior as well as to allow an individual to easily move about withinthe interior.

Hydroponics has gained popularity for use in growing plants within agreenhouse. In many instances, plant yields using hydroponics areequivalent to those for plants grown in fertile soil. However, theplacement of the large hydroponic tanks containing the solution forproviding nutrients to the plants is a problem. To avoid detracting fromthe space available for hydroponic plant growth and to avoid inhibitingthe movement of workers within the greenhouse, the tanks are oftenlocated outside the greenhouse. Thus, the solution in the tanks may needto be heated or cooled before feeding the plants. Such heating andcooling consumes energy which results in increased costs. Therefore, itis desirable to provide a greenhouse in which the hydroponic solutiontanks are positioned within the interior of the greenhouse such that thesolution does not need to be heated or cooled before feeding the plantsand such that the tanks do not significantly reduce the number of plantsthat may be grown within the greenhouse's interior space.

OBJECTS OF THE INVENTION

One object of the invention is to provide a greenhouse which is able tooptimize the amount of sunlight required for the growth of the plantstherein as well to retain the heat within the greenhouse according toprescribed optimum conditions for the types of plants within thegreenhouse.

Another object of the invention is to provide an auxiliary means forheating and cooling the interior of a greenhouse which is notprohibitively expensive to operate, is inexpensive to maintain, andwhich requires little maintenance or repair.

Another object of the invention is to provide an auxiliary heatingand/or cooling system which is a closed system.

Still another object of the present invention is to provide a greenhousewhose contents are arranged to permit easy access to the plants withinthe interior as well as to allow an individual to easily move aboutwithin the interior.

Yet another object of the present invention is to provide a greenhousein which the hydroponic solution tanks are positioned within theinterior of the greenhouse such that the solution does not need to beheated or cooled before feeding the plants and such that the tanks donot significantly reduce the number of plants that may be grown withinthe greenhouse's interior space.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a partial cross-sectional view of one embodiment of thewest end of the greenhouse of the present invention in which the panelswithin the upper interior portion of the greenhouse are in the lighttransmissive position and the pivotable exterior panel is in its open,or reflective, position.

FIG. 2 shows a partial cross-sectional view of the embodiment of FIG. 1in which the panel within the upper interior portion of the greenhouseis in its insulative position and the pivotable exterior panel is in itsclosed, or insulative, position.

FIG. 3 shows a top view of one embodiment of the interior of thegreenhouse of the present invention.

FIG. 4 shows a side view of one embodiment of the heat exchanger of thepresent invention.

FIG. 5 shows an end view of the heat exchanger of the embodiment of FIG.4.

SUMMARY OF THE INVENTION

A greenhouse and a method for controlling the environment of theinterior space of the greenhouse is disclosed. The greenhouse includesan interior insulative panel and an exterior reflective panel capable ofinsulating the interior of the greenhouse and reflecting sunlight intothe interior. The greenhouse also includes a closed-system heatexchanger having a plurality of spaced water-impermeable water flowpassageways through which water flows by gravitational forces and havinga means for blowing air between the water flow passageways such that theair does not contact the water and such that the air is either heated orcooled by the water. In addition, the heat exchanger may include a waterdischarge and/or a gas discharge for the control of humidity and gaslevels within the greenhouse. Finally, the greenhouse includeshydroponic plant beds disposed on top of the heat exchangers andhydroponic solution tanks along the outer interior walls of thegreenhouse. The floor plan of the greenhouse allows easy access to allplants and assists in maintaining the temperature within the greenhousedue to the presence of the hydroponic solution tanks withoutsignificantly reducing the area available for plants. Such a greenhouseis inexpensive to operate and maintain and may be used to extend thegrowing season of seasonal plants throughout the calendar year.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a partial cross-sectional view ofone embodiment of the west end of the greenhouse of the presentinvention in which the panels within the upper interior portion of thegreenhouse are in the light transmissive position and the pivotableexterior panel is in its open, or reflective, position. The interiorspace of greenhouse 10 is defined by first and second opposing interiorwalls 11, 12, respectively. First and second interior walls 11, 12 arepositioned with respect to each other such that first and second bases13, 14 are separated by a greater distance than are first and secondtops 15, 16. Translucent ceiling 19 divides the interior of greenhouse10 into upper portion 20 and lower portion 21. Within upper portion 20of greenhouse 10 are first and second insulative panels 22 and 23suspended from the interior walls 11, 12 by first and second adjustingmeans 24 and 25, respectively, which may comprise, for example, a pulleyattached to first or second interior walls 11, 12 and a rope connectedto first or second insulative panels 22 or 23. First and secondinsulative panels 22, 23 are shown in FIG. 1 in the light transmissiveposition in which first and second insulative panels 22, 23 are spacedfrom translucent ceiling 19 to allow sunlight to enter lower portion 21from upper portion 20 through translucent ceiling 19.

Greenhouse 10 comprises north and south exterior edges, 17, 18,respectively, as well as east and west exterior edges (not shown).Greenhouse 10 also includes pivotable panel 26 positioned along southexterior edge 18 of greenhouse 10. Pivotable panel 26 is connected tosouth exterior edge 18 by hinge 27 and third adjusting means 28. In FIG.1, pivotable panel 26 is shown in its open, or reflective, positions inwhich pivotable panel 26 is angled with respect to south exterior edge18 of greenhouse 10.

Also located within greenhouse 10 near tops 15, 16 of first and secondinterior walls 11, 12 is light 60. Light 60 may be used to assist inproviding the optimal light conditions within the interior space ofgreenhouse 10 required for plant growth therein. Light 60 may beparticularly useful in low natural sunlight conditions and may also beused to illuminate the interior of greenhouse 10 during nighttime hours.Along the west end of greenhouse 10, as shown, are windows 61-64. Firstand second windows 61, 62 are positioned above translucent ceiling 19 toprovide access to upper interior portion 20. Third and fourth windows63, 64 are positioned below translucent ceiling 19 to provide access tolower interior portion 21.

FIG. 2 shows a partial cross-sectional view of the embodiment of FIG. 1in which the panel within the upper interior portion of the greenhouseis in its insulative position and the pivotable exterior panel is in itsclosed, or insulative, position. In this configuration of greenhouse 10,first and second insulative panels 22, 23 have been adjusted by firstand second adjusting means 24, 25 to be placed in a position in whichfirst and second insulative panels 22, 23 substantially covertranslucent ceiling 19. When in the insulative position, first andsecond insulative panels 22, 23 assist in maintaining the temperaturewithin lower interior portion 21 as well as to limit the amount ofsunlight entering lower portion 21.

In FIG. 2, pivotable panel 26 is in its closed, or insulative position,in which pivotally panel 26 is substantially flush against southexterior wall 18 of greenhouse 10. In its closed position, pivotablepanel 26 assists in maintaining the temperature within lower portion 21of greenhouse 10 as well as to limit the amount of sunlight enteringlower portion 21.

It will be appreciated by those of skill in the art that the positioningof first and second insulative panels 22, 23 and pivotable panel 26 maybe adjusted to various positions between those described above by usingfirst, second and third adjustments means 24, 25 and 28, respectively.Thus, adjustments may be made for a multitude of sunlight conditions andexterior temperature conditions, thereby limiting the need for auxiliaryheating or cooling in many instances. Generally, auxiliary heating andcooling is only required under extreme conditions, such as extremelycold exterior temperatures coupled with limited sunlight or extremelyhot exterior conditions coupled with intense sunlight.

Returning to FIG. 1, first and second heat exchangers 30, 31 each havingupper surface 32, 33, respectively, are positioned within lower interiorportion 21 of greenhouse 10. First and second heat exchanger 30, 31,described in greater detail herein, are capable of heating and coolinglower interior portion 21 of greenhouse 10. Positioned above first andsecond upper surfaces 32, 33 are first and second hydroponic plantgrowing means 34, 35, respectively. First and second upper surfaces 32,33 also serve as first and second hydroponic growing tables for thesupport of hydroponic growing means 34, 35 thereon. First and secondhydroponic plant growing means 34, 35 are operatively connected to andprovided with hydroponic solution from first and second hydroponicsolution tanks 36 and 37, respectively, which are positioned such thatthey abut first and second opposing interior walls 11, 12. Positionedabove first and second hydroponic plant growing means 34, 35 are firstand second conveyor means 38, 39, respectively. First and secondconveyor means 38, 39 may be used to transport plants or fruit removedfrom plants from first and second hydroponic growing means 34, 35 toanother location within greenhouse 10.

It will be appreciated by those of skill in the art that the position offirst and second hydroponic tanks 36, 37 within greenhouse 10 assists inmaintaining the desired temperature within lower interior portion 21 ofgreenhouse 10 as they serve as a large thermal mass. In addition, thesolution within first and second hydroponic tanks 36, 37 is of atemperature conducive to plant growth and does not require that a meansbe provided to heat or cool the solution as may be required should thetanks be located outside greenhouse 10.

Referring to FIG. 3, there is shown a top view of one embodiment of theinterior of the greenhouse of the present invention. Positioned alongand abutting first opposing interior wall 11 are first and thirdhydroponic solution tanks 36, 40. Similarly, positioned along andabutting second interior wall 12 are second and fourth hydroponicsolution tanks 37, 41. Cross isle 42, disposed between first and thirdhydroponic solution tanks 36, 40 and between second and fourthhydroponic solutions tanks 37, 41, allows a person within greenhouse 10to traverse the center of greenhouse 10 between first and secondinterior walls 11, 12. Also located within greenhouse 10 are first,second, third and fourth hydroponic growing tables 34, 35, 43 and 44,respectively, which are operatively connected to first, second, thirdand fourth solution tanks 36, 37, 40, 41 via first, second, third andfourth connection means 50-53, respectively. In this embodiment, first,second third and fourth growing tables 34, 35, 43 and 44 comprise theupper surface of a temperature control means, or heat exchanger, asillustrated in FIG. 1. First and second hydroponic growing tables 34, 35are disposed between first and second hydroponic solution tanks 36, 37to permit easy access to all plants within greenhouse 10. Specifically,first growing table 34 is spaced from first solution tank 36 to formfirst longitudinal isle 45 which permits a person to be positionedtherebetween. Second growing table 35 is space from second solution tank37 to form second longitudinal isle 46 which permits a person to bepositioned therebetween. Also, first growing table 34 is spaced fromsecond growing table 35 to form third longitudinal isle 47 which permitsa person to be positioned therebetween. In this embodiment, a similararrangement exists for third and fourth hydroponic solution tanks 40, 41and third and fourth hydroponic growing tables 43, 44 such that thirdsolution tank 40 is spaced from third growing table 43 to form firstlongitudinal isle 45, fourth solution tank 41 is spaced from fourthgrowing table 44 to form second longitudinal isle 46, and third andfourth growing tables 43, 44 are spaced from each other to form thirdlongitudinal isle 47. Also, growing tables 34, 35, 43, 44 are spacedsuch that cross isle 42 is formed between first and third growing tables34, 43 and between second and fourth growing tables 35, 44.

It will be appreciated by those of skill in the art that the floor planof the greenhouse in the embodiment of FIG. 3 is such that a person isable to access all plants within greenhouse 10 residing on growingtables 34, 35, 43, 44. In addition, the presence of hydroponic solutiontanks 36, 37, 40, 41 does not impede a person from moving withingreenhouse 10 nor do they significantly reduce the amount of areaavailable for growing plants.

As shown in FIGS. 2 and 3, first, second, third and fourth conveyormeans 38, 39, 48, and 49, respectively, are positioned above first,second, third and fourth growing tables 34, 35, 43 and 44, respectively.Fruits or plants from first and third growing tables 34, 43 may betransported via first and third conveyor means 38, 48 to firstcollection means 54 and fruits or plants from second and fourth growingtables 35, 44 may be transported via second and fourth conveyor means39, 49 to second collection means 55.

It will be appreciated by those of skill in the art that first, second,third and fourth conveyor means 38, 39, 48, 49 provide a means by whichfruits from plants may be quickly collected at a central location.

In one embodiment of the greenhouse of the present invention, the heightof first and second hydroponic solution tanks 36, 37 is two (2) feet andthe angle of exterior walls 17, 18 is 60° such that exterior walls 17,18 reach a height of 16 feet above ground level. Thus, the width ofgreenhouse 10 is 17 feet. The height of first and second heat exchangers30, 31 is two (2) feet and first and second conveyor means arepositioned approximately three (3) feet above first and second heatexchangers 30, 31. Translucent ceiling 19 is eight (8) feet above groundlevel. The total length of greenhouse 10, as shown in FIG. 3, is 150feet with heat exchangers 30, 31, the heat exchangers (not shown) belowhydroponic growing tables 43, 44 and hydroponic solution tanks 36, 37,40, 41 each being 72 feet in length. Thus the base dimensions ofgreenhouse 10 are 17 feet by 150 feet.

It will be appreciated by those of skill in the art that the dimensionsof the greenhouse may be revised according to the number and type ofplants to be grown within the greenhouse. Of course, the volume of thegreenhouse of the present invention must be appropriate to allowsufficient heating and/or cooling as well as to provide appropriatelevels of sunlight depending on the climate in which the greenhouse isinstalled.

FIG. 4 shows a side view of one embodiment of the heat exchanger of thepresent invention. Heat exchanger 30 has upper surface 32 above which ispositioned hydroponic plant growing means 34. Within heat exchanger 30is a plurality of spaced water-impermeable water flow means 90. Eachwater flow means 90 includes water inlet end 91 adapted to receive waterfrom an external water source (see FIG. 5) as well as water outlet end92 adapted to discharge water. Also, each water flow means 90 isdisposed such that gravity causes water introduced through water inletend 91 to flow to water outlet end 92. In one embodiment, water inletend 91 may comprise, for example, an aperture in tubing into which wateris introduced (see FIG. 5) and water outlet end 92 may comprise, forexample, a trough into which water from water flow means 90 iscollected. Such troughs may be connected to a common drain.

Heat exchanger 30 also includes air inlet 93 and air outlet 94,positioned such that air flowing from air inlet 93 to air outlet 94moved between spaced water flow means 90. To blow air from air inlet 93toward air outlet 94, heat exchanger 30 also includes fan 65.

Each water flow means 90 includes interior passageway 71 through whichwater flows and which does not contact the air flowing from air inlet 93to air outlet 94. In this embodiment, each water flow means 90 includespolyurethane plastic sheet 66 wrapped around corrugated sheet 67, waterinlet end 91 and water outlet end 92 and affixed to corrugated sheet 67at first and second connection points 68 and 69. Corrugated sheet 67 isformed to provide passageway 71 (see FIG. 5).

It will be appreciated by those of skill in the art that little externalenergy is required to operate the heat exchanger of the presentinvention. In some manner, water must be provided to heat exchanger 30and therefore may require energy to pump the water from the water supply(see FIG. 5). The only other energy consuming component of heatexchanger 30 is fan 65. Therefore, heat exchanger 30 is inexpensive tooperate. In addition, the number and type of components which compriseheat exchanger 30 are such that heat exchanger 30 is inexpensive tomaintain and requires little maintenance or repair.

It will also be appreciated that the heat exchanger of the presentinvention is a closed system. Heat exchanger 30 operates withoutrequiring that air from the exterior of the greenhouse be used tomaintain a constant temperature in the greenhouse. Thus, greatercontrol, at less expense, over the interior space of greenhouse 10 isachieved than with auxiliary heating and cooling systems which requireexternal air to be brought into greenhouse 10.

In addition to serving as a temperature control means, heat exchanger 30may be used to control humidity and the level of various gases withingreenhouse 10. Referring to FIG. 4, water discharge means 72, shown inthis embodiment to be positioned near air outlet 94, is adapted todischarge water into air flowing toward air outlet 94 to therebyhumidify air entering the interior space of greenhouse 10. A similar gasdischarge means (not shown) may be included in heat exchanger 30 tointroduce carbon dioxide, or other desired gases, into air flowingtoward air outlet 94 to thereby control the level of gases within theinterior space of greenhouse 10.

Referring to FIG. 5, there is shown an end view of the heat exchanger ofthe embodiment of FIG. 4. In this embodiment, water is supplied to heatexchanger 30 from water source 80. Water is moved from water source 80through water transfer means 82 into interior passageways 71 of waterflow means 90 through water inlet end 91. Water flow means 90 maycomprise, for example, copper tubing and water inlet end 91 may be anaperture within the tubing. Valve 81 provides a means for variablycontrolling the amount of water introduced into water inlet end 91 tothereby affect the degree to which temperature of air flowing withinheat exchanger is changed by the temperature of water flowing withinwater flow means 90.

It will be appreciated by those of skill in the art that water source 80may comprise water from a natural source. Such water is oftenapproximately 55° F. in temperature. Thus, if the interior space ofgreenhouse 10 is less than 55° F., the air flowing within heat exchanger30 will be warmed toward 55° F., or, if the interior space of greenhouse10 is greater than 55° F., the air flowing within heat exchanger 30 willbe cooled toward 55° F.

To control the environment within the greenhouse of the presentinvention, a water source is provided to water inlet end 91 and drainedinto water outlet end 92. Air is forced between spaced flow means 90such that the temperature of the air at air outlet 94 is closer to thetemperature of water than it is at air inlet 93.

It will be appreciated by those of skill in the art that the operationof heat exchanger 30, first and second insulative panels 22, 23 andpivotable exterior panel 26 results in an environment in which thetemperature, humidity and gas levels of the interior space of greenhouse10 may be precisely controlled to allow greenhouse 10 to be used to growplants, such as strawberries, which are ordinarily very seasonal as theyrequire a particular set of environmental conditions for growth of theplant and any fruit which the plant may bear.

I claim:
 1. A method for controlling the environment within agreenhouse, comprising the steps of:(a) providing a greenhouse havingwalls defining an interior space and exterior edges, a heat exchangerand a hydroponic plant growing means, the heat exchanger having an uppersurface, the hydroponic plant growing means positioned above the uppersurface of the heat exchanger, and the heat exchanger comprising:(i) aplurality of spaced water-impermeable flow means having first and secondopposing ends defining a length of the flow means, a width of the flowmeans being less than the length of the flow means, each flow meanscomprisinga water inlet end adaptive to receive water, and a wateroutlet means adaptive to discharge water, and each flow means beingdisposed such that gravity may cause water to flow from the inlet endtoward the outlet means; (ii) an air inlet and an air outlet, positionedsuch that air flowing from the air inlet to the air outlet moves betweeneach of said flow means, wherein each of said flow means furthercomprises an interior passageway in which water flows, and wherein airflowing from the air inlet to the air outlet between the flow means doesnot contact water in said interior passageway, and (iii) a fan adaptedto move air from the air inlet toward the air outlet, the fan positionedat one end of the flow means and oriented to move air toward an oppositeend of the flow means; (b) providing a water source to the water inletend; (c) draining water into the water outlet means; and (d) forcing airbetween the flow means such that the temperature of the air at the airoutlet is closer to the temperature of provided water than the air atthe air inlet.
 2. The method of claim 1 wherein the greenhouse furthercomprises a translucent ceiling within the interior space such that thetranslucent ceiling divides the interior space into upper and lowerportions and at least one panel in the upper portion is movable betweenan insulative position in which the panel substantially covers thetranslucent ceiling and a light transmissive position in which the panelis spaced from the translucent ceiling, further comprising the stepof:(e) adjusting the panel between the insulative position and the lighttransmissive position.
 3. The method of claim 1 wherein the greenhousefurther comprises at least one panel pivotally positioned along oneexterior of the greenhouse, the panel being movable between a closedposition in which the panel is substantially flush against thegreenhouse, and an open position in which the panel is at an acute anglewith respect to the exterior d of the greenhouse, further comprising thestep of:(e) adjusting the exterior panel between its closed position andits open position.
 4. The method of claim 1 wherein the heat exchangerfurther comprises at least one water discharge means adapted todischarge water into air flowing toward the air outlet to therebyhumidify the interior space, further comprising the step of:(e)discharging water into the air flowing toward the air outlet.
 5. Themethod of claim 1 wherein the heat exchanger further comprises carbondioxide introduction means for introducing carbon dioxide into airflowing toward the air outlet, and further comprising the step of:(e)introducing carbon dioxide into the carbon dioxide introduction means.6. The method of claim 1 wherein the greenhouse further comprises an airduct means positioned to receive air from the air outlet and direct airtoward the hydroponic plant growing means.